Angular acceleration sensors are used in diverse fields of technology. They can be used in electric tools, for example, and make it possible to monitor an angular acceleration limit for the electric tool, for example a drill. If an overshoot is detected, the electric tool is then switched off. Moreover, angular acceleration sensors are for example also used in the field of video cameras for the purpose of vibration stabilization.
In this case, angular acceleration sensors can be based on the principle that a seismic mass is deflected on account of the angular acceleration and the deflection of the seismic mass is measured. An angular acceleration acting on the seismic mass can then be deduced on the basis of the measured deflection of the seismic mass.
In order to detect a deflection, piezoresistive elements, for example, can be arranged, which are expanded or compressed during a deflection. The piezoresistive elements change their resistance in this case. An angular acceleration acting on the seismic mass can then be deduced on account of the change in the resistance of the piezoresistive elements.
One method for producing a piezoresistive angular acceleration sensor was disclosed for example in the report “A structure of angular acceleration sensor using silicon cantilevered beam with piezoresistors”, IEEE Conference on Industrial Electronics, Control, Instrumentation, and Automation, 1992.
U.S. Pat. No. 4,996,878 A disclosed a transducer element for measuring linear and angular accelerations. For this purpose, the transducer element comprises two electro-mechanically acting oscillating beams fixed with respect to a predetermined main axis on a substrate by means of fixing elements. Electrical output signals proportional to a flexure of the beams upon rotation about the main axis are fed to a signal processing circuit, which is designed such that, with identical or opposite polarity of the oscillating beams, a summing amplifier determines the linear acceleration along the z-axis and a differential amplifier determines the angular acceleration about the y-axis. The oscillating beams can be embodied as piezoelectric bending elements or as bending elements coated with piezoresistive semiconductors.
A further angular acceleration sensor was disclosed in GB 1,344,811 A. In this case, the angular acceleration sensor comprises an annular conduit with an electrically non-conductive fluid, at least one barrier in said conduit, such that at least two ends are provided for said conduit, a pair of electrical or piezoresistive elements for each conduit end, wherein one is respectively arranged adjacent to said conduit ends and wherein said elements are arranged in the conduit in this way in order to be subjected to pressure changes in said fluid. The angular acceleration can then be deduced from the pressure changes by means of the resistance changes.
WO 09109969 A disclosed an angular rate sensor device. The angular rate sensor device in this case comprises a disk-shaped structure having a region for a seismic mass and a flexible region. The disk-shaped structure is connected to a substrate in a manner enabling a wave-type precession motion and such that during the wave-type precession motion the material of the seismic mass performs elliptic motion.
JP 2008/107257 A disclosed an acceleration sensor for measuring a linear acceleration and an angular acceleration. The sensor substantially comprises a rectangular frame, in the center of which a seismic mass is arranged. The seismic mass is connected to the rectangular frame by means of beams running perpendicularly to the respective sides. In the end region of two beams arranged on the frame, two piezoresistive elements for measuring the angular acceleration are arranged in each case obliquely with respect to one another.